/*
     File: CustomHTTPProtocol.h
 Abstract: An NSURLProtocol subclass that overrides the built-in HTTP/HTTPS protocol.
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 */

#import <Foundation/Foundation.h>

@protocol CustomHTTPProtocolDelegate;

@interface CustomHTTPProtocol : NSURLProtocol

// Subclass specific additions

+ (void)start;
    // Call this to start the module.  Prior to this the module is just dormant, and 
    // all HTTP requests proceed as normal.  After this all HTTP and HTTPS requests 
    // go through this module.

// The delegate is not retained in general, but is retained for the duration of any given 
// call.  Once you set the delegate to nil you can be assured that it won't be called 
// unretained (that is, by the time that -setDelegate: returns, we've already done 
// all possible retains on the delegate).

+ (id<CustomHTTPProtocolDelegate>)delegate;
+ (void)setDelegate:(id<CustomHTTPProtocolDelegate>)newValue;

@property (atomic, retain, readonly ) NSURLAuthenticationChallenge *    pendingChallenge;   // main thread only please

- (void)resolveAuthenticationChallenge:(NSURLAuthenticationChallenge *)challenge withCredential:(NSURLCredential *)credential;
    // must be called on the main thread
    // credential may be nil, to continue the request without a credential

@end

/*
    The delegate handles two different types of callbacks:

    o authentication challenges
    o logging

    The latter is very simple.  The former is quite tricky.  The basic idea is that each CustomHTTPProtocol 
    sends the delegate a serialised stream of authentication challenges, each of which it is expected to 
    resolve.  The sequence is as follows:

    1. It calls -customHTTPProtocol:canAuthenticateAgainstProtectionSpace: to determine if your delegate 
       can handle the challenge.  This can be call on an arbitrary background thread.

    2. If the delegate returns YES, it calls -customHTTPProtocol:didReceiveAuthenticationChallenge: to 
       actually process the challenge.  This is always called on the main thread.  The delegate can resolve 
       the challenge synchronously (that is, before returning from the call) or it can return from the call 
       and then, later on, resolve the challenge.  Resolving the challenge involves calling 
       -[CustomHTTPProtocol resolveAuthenticationChallenge:withCredential:], which also must be called 
       on the main thread.  Between the calls to -customHTTPProtocol:didReceiveAuthenticationChallenge: 
       and -[CustomHTTPProtocol resolveAuthenticationChallenge:withCredential:], the protocol's 
       pendingChallenge property will contain the challenge.
    
    3. While there is a pending challenge, the protocol may call -customHTTPProtocol:didCancelAuthenticationChallenge: 
       to cancel the challenge.  This is always called on the main thread.
*/

@protocol CustomHTTPProtocolDelegate <NSObject>

@optional

- (BOOL)customHTTPProtocol:(CustomHTTPProtocol *)protocol canAuthenticateAgainstProtectionSpace:(NSURLProtectionSpace *)protectionSpace;
    // called on an arbitrary thread
    // protocol will not be nil
    // protectionSpace will not be nil
    
- (void)customHTTPProtocol:(CustomHTTPProtocol *)protocol didReceiveAuthenticationChallenge:(NSURLAuthenticationChallenge *)challenge;
    // called on the main thread
    // protocol will not be nil
    // challenge will not be nil
    
- (void)customHTTPProtocol:(CustomHTTPProtocol *)protocol didCancelAuthenticationChallenge:(NSURLAuthenticationChallenge *)challenge;
    // called on the main thread
    // protocol will not be nil
    // challenge will not be nil

- (void)customHTTPProtocol:(CustomHTTPProtocol *)protocol logWithFormat:(NSString *)format arguments:(va_list)argList;
    // called on an arbitrary thread
    // protocol may be nil, implying a log message from the class itself
    // format will not be nil

@end
